This invention relates to instruments, and more specifically to an instrument which based on a theory that two columns of liquid with two different densities and a common pressure reference point will have two different column levels is operative to measure the presence of suspended solids in a fluid substance.
One of the important parameters in many processes is that of the extent to which there are particles present in a fluid substance. As such, it has long been known in the prior art to provide instruments that are capable of being employed for purposes of effecting measurements of particles. To this end, the prior art is replete with examples of various types of instruments that have been utilized heretofore for purposes of obtaining particle measurements. In this regard, in many instances discernible differences exist in the technique by which the measurement of the particles is accomplished. The existence of such differences is, in turn, attributable for the most part to the diverse functional requirements that are associated with the specific application in which such instruments are intended to be employed. For instance, in the selection of the particular type of instrument that is to be utilized for a specific application one of the principal factors to which consideration must be given is that of the nature of the substance of which the particle that is to be measured is composed. Another factor to which consideration must be given is that of the nature of the substance in which the particles are present at the time they are being measured. Yet another factor to which consideration must be given is the relative size of the particles that are to be measured.
Some of the techniques that have been utilized heretodate by the prior art for purposes of accomplishing the measurement of particles include acoustical techniques, optical counting techniques, electrical counting techniques, sedimentation techniques, separation techniques, and surface measurement techniques. Moreover, the kinds of particles with which such techniques have been sought to be applied for purposes of making measurements of the particles include such particles as mineral particles, chemical particles, food particles, blood particles as well as others. In addition, diverse ones of the techniques to which reference has been had hereinbefore have been sought to be employed for purposes of accomplishing the measurement of particles while the latter are present in a variety of different types of fluid substances such as various types of liquids and various types of gases.
One type of process in which the amount of particles that are present in a fluid substance is known to be an important consideration for the successful operation of the process is that process which is utilized in conjunction with wet scrubber applications. In such applications, there exists a need to know to what extent particles are present in a limestone slurry. To this end, there is a need to be able to measure the percent of suspended solids that are present in the limestone slurry. One instrument that those in the prior art have attempted to utilize for purposes of measuring the percent of suspended solids that are present in the limestone slurry is that referred to in the industry as a hydrometer and more specifically as a floating hydrometer. The floating hydrometer works on a theory that two columns of liquids with two different densities and a common pressure reference point will have two different column levels. This theory can be made to work with limestone slurry because if the slurry is not agitated the suspended solids, which make up the majority of the solids, will precipitate out of the liquid such that the liquid which remains has almost the same density as clear water.
Insofar as the nature of the construction thereof is concerned, the floating hydrometer basically resembles a float having a long piece of pipe or cylinder stuck through the middle thereof. The object which is sought to be achieved therewith is to have the pipe or cylinder, by virtue of its relatively long length, function to eliminate agitation of the liquid to a sufficient extent that the suspended solids will fall out of the bottom of the pipe or cylinder. At the top of the pipe or cylinder there is mounted a level probe. Thus, by knowing the level at which the float sits on the liquid, the length of the pipe or cylinder and the densities of the liquid inside and outside of the pipe or cylinder, a difference in level read by the level probe can be calculated for a desired change in percent solids.
Unfortunately, however, when measurements were sought to be made with a floating hydrometer that embodies the form of construction and the mode of operation, which has been described hereinbefore, the results that were obtainable therewith were found to be unacceptable. Namely, it was found that the measurements obtained through the use of such a floating hydrometer were inconsistent. That is, it was found that the measurements obtained through the use of such a floating hydrometer were not consistent when compared to the actual solids known to be present in the reaction tank wherein measurements were sought to be made of the percent of suspended solids in the limestone slurry.
In an effort to overcome this problem of inconsistent measurements being obtained when the floating hydrometer was used to measure the percent of suspended solids in the limestone slurry, one thing which was attempted was that of purging the float, as the latter was being lowered into the reaction tank, for a period of several hours with clean water so as to wash out therefrom any solids that might otherwise be present. Upon trying this, it was found that when the purge water was shut off, the measurements obtained with the floating hydrometer would track the actual reaction tank solids relatively closely for several hours. After some time, however, the floating hydrometer would once again begin to produce erratic measurements that did not correlate with the actual solids in the reaction tank. The extent of the discrepancy which existed between the measurements obtained with the floating hydrometer and the actual solids in the reaction tank appeared to vary depending on the level of the fluid substance in the reaction tank and the number of spray pumps in service in the primary reaction tank.
There were thought to be two possible reasons why the measurements obtained through the use of a floating hydrometer that embodies the nature of the construction and the mode of operation which has been described hereinbefore were found to be inconsistent. The first is thought to reside in the fact that the constant up and down motion, i.e., bobbing, of the floating hydrometer caused by the choppy surface that exists in the reaction tank could conceivably produce sufficient agitation inside the pipe or cylinder of a floating hydrometer to keep suspended solids present in the liquid that is contained within the pipe or cylinder of the floating hydrometer. The other possible explanation for the erratic measurement is that a high volume of liquid flowing at a ninety degree angle past the bottom end of the pipe or cylinder of the floating hydrometer could pull a slight negative pressure inside the pipe or cylinder of the floating hydrometer. The existence of such a slight negative pressure within the pipe or cylinder of a floating hydrometer would tend to lower the internal column height of the liquid therewithin and thereby give rise to erroneous outputs from the floating hydrometer. In this connection, the spray pumps associated with a reaction tank wherein measurements of the percent suspended solids in limestone slurry are sought to be obtained are known to be operative to pump at a rate of 18,500 gallons per minute. Thus, with four pumps in service in a reaction tank, there could very possibly be enough flow past the bottom end of the pipe or cylinder of the floating hydrometer to cause such a condition to exist wherein a slight negative pressure was produced within the pipe or cylinder of the floating hydrometer.
A need has, therefore, been evidenced in the prior art for a new and improved form of floating hydrometer of the type that is operative based on a theory that two columns of liquid with two different densities and a common pressure reference point will have two different column levels. Further, a need has been evidenced for such a new and improved floating hydrometer which would not suffer from the problem of inconsistent measurements that heretodate has served to disadvantageously characterize the performance of prior art forms of floating hydrometers. Moreover, a need has been evidenced for such a new and improved floating hydrometer that would be capable of operation to dissipate the fluid energy occasioned by the bobbing motion to which the float portion of the floating hydrometer is known to be subjected when positioned within a reaction tank. In addition, a need has been evidenced for such a new and improved floating hydrometer that would also be capable of operation as a vacuum break whereby should a slight negative pressure be produced within the floating hydrometer, there will be made to occur an equalization of this negative pressure.
It is, therefore, an object of the present invention to provide a new and improved form of instrument suitable for use for purposes of measuring the presence of particles in a fluid substance.
It is another object of the present invention to provide such an instrument which is particularly suited for employment for purposes of obtaining measurements as to the percent of suspended solids that are in a limestone slurry.
It is still another object of the present invention to provide such an instrument wherein the instrument comprises a floating hydrometer.
A further object of the present invention is to provide such a floating hydrometer which works on the theory that two columns of liquid with two different densities and a common pressure reference point will have two different column levels.
A still further object of the present invention is to provide such a floating hydrometer which is advantageously characterized by the fact that consistent measurements can be obtained through the use thereof notwithstanding the effects of fluid energy.
Yet another object of the present invention is to provide such a floating hydrometer which is advantageously characterized by the fact that consistent measurements can be obtained through the use thereof notwithstanding the effects of negative pressure.
Yet still another object of the present invention is to provide such a floating hydrometer which is relatively easy to employ as well as being relatively inexpensive to provide.